The present invention pertains to a clamping element for clamping workpieces on machine tables, devices or pallets by means of a tiltably mounted clamping lever, which is displaceable in a clamping plane.
The clamping of workpieces on machine tables and the like requires clamping elements that have a large free space in order to change the workpiece without having to remove the clamping lever. In addition, the clamping levers must be able to be adapted to the particular workpiece inserted. This is achieved, on the one hand, by changing the clamping levers that are available in different sizes, and, on the other hand, by means of clamping levers that are mounted such that they can be adapted in their length to the workpiece.
The forces that are generated by the machining of the workpieces may be very strong and must be reliably absorbed by the clamping levers and their bearings. Changes in the cross section on the clamping levers due to the introduction of longitudinal slots for the longitudinal displacement have an adverse effect on the transmission of forces. Moreover, longitudinal slots are subject to risks of contamination due to flying chips.
It has been known (VDI-Verlag, 1992, p. 489, Devices, Efficient Planning and Design) that a clamping element can be provided with a clamping lever that is held by a screw. This screw is provided with a conical socket, which is mounted in a spherical disk. The clamping lever is provided with a longitudinal slot, by which the screw is guided. This longitudinal slot leads to a substantial weakening of the cross section of the clamping lever; in addition, the center of gravity for the clamping lever is located too high due to the spherical disk lying on the clamping lever and the conical socket of the screw, so that force components acting obliquely on the workpiece cannot be ruled out, which may lead to tearing of the workpiece. The longitudinal slot is, furthermore, exposed to contamination by chips during machining, which contributes to difficulties in the return of the clamping lever.
Such an arrangement is also associated with problems if the clamping lever is provided with a pressing screw for adaptation to different workpiece heights. To remove such a clamping lever from the range of action of the workpiece, the center of gravity must be located far away from the workpiece, as a result of which the clamping lever must be made very long, which has an unfavorable effect on the transmission of forces. The screw connection formed by the spherical disk and the conical socket is, moreover, elastic, so that the workpiece is supported insufficiently under the action of transverse forces as a consequence of machining.
The object of the present invention is to design a clamping element such that the clamping lever has a pivotable design and is mounted displaceably in its longitudinal direction, but does not protrude from the clamping element in its starting position regardless of its length if a pressing screw is provided for adaptation to different workpiece heights.
According to the invention a clamping element for clamping workpieces on machine tables and the like is provided with a tiltably mounted clamping lever, which is arranged longitudinally displaceably in a clamping plane. A housing is provided with a fork head. In the forks of the fork head a hole is milled approximately centrally. A rotatably mounted king pin is inserted into each hole.
The advantage of this solution relates to an extremely stable mounting of the clamping lever. Transverse forces as a consequence of machining do not affect the clamping unit. In addition, the design permits small dimensions in the direction of the slide and consequently it makes it possible to eliminate disturbing edges for machining tools.
The king pin may have a guide pin provided with two flattened areas located opposite each other in the form of guide surfaces. The diameter of the guide pin may be smaller than, equal to or greater than the diameter of the king pin.
The clamping lever may have a square cross section with a guide grooves on opposite sides. The guide grooves may open at both ends of the clamping lever. The guide grooves may be milled on two opposite sides. The clamping lever can be fixed by means of a lock screw and its position can be defined by a pin.
The guide groove of the clamping lever and the guide surfaces of the guide pin may be coordinated with one another.
The fork head may be equipped with the king pins provided as two rotatably mounted king pins in holes. The guide pins of the king pins may protrude with guide surfaces into the space between the forks. The clamping lever can be inserted into the fork head and can be attached to the guide surfaces with its grooves and may be guided longitudinally displaceably and can be tilted around the central axis of the king pins.
The longitudinally displaceable and tiltable clamping lever can be brought hydraulically into its clamping position by means of a piston.
The clamping lever on the clamping head may be equipped with a pressing screw. The clamping lever may be introduced into the housing in a released state.
A pocket may be formed in the housing as a free space for the pressing screw fastened to the head of the clamping lever.
Sensors for monitoring the position of the clamping lever may be provided on the housing.
The present invention is described in greater detail in the figures. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.